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ABOUT THIS IMAGE:

These images show four spiral galaxies with bars of stars and gas slicing through them.

The galaxies are at various distances from Earth. The galaxy at upper left is 2.1 billion light-years away; the galaxy at upper right, 3.8 billion light-years away; the galaxy at lower left, 5.3 billion light-years away; and the galaxy at lower right, 6.4 billion light-years away.

The galaxies are part of a landmark study of more than 2,000 spiral galaxies from the largest galaxy census conducted by the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope.

The survey's results show that so-called barred spiral galaxies were far less plentiful over the last 7 billion years than they are today, in the local universe. The study's results confirm the idea that bars are a sign of galaxies reaching full maturity as the "formative years" end. The observations are part of the Cosmic Evolution Survey (COSMOS).

COSMOS covers an area of sky nine times larger than the full Moon, surveying 10 times more spiral galaxies than previous observations.

Astronomers assembled these images from observations taken with Hubble and the Subaru Telescope in Mauna Kea, Hawaii.